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Oct. 20, 2009 (Philadelphia) -- Women who spray their homes and gardens with
insecticides may be placing themselves at risk for rheumatoid arthritis and
lupus, a study shows.

In a study of more than 75,000 women, those who used insecticides six
or more times a year had nearly two-and-a-half times the risk of developing the
autoimmune diseases than women who adopted a live-and-let-live attitude toward
bugs.

Similarly, the risk more than doubled if bug sprays were used in the home
for 20 or more years.

Hiring a gardener or commercial company to apply insecticides also resulted
in a doubling of risk, but only if they were used long-term, says Christine G.
Parks, PhD, an epidemiologist with the National Institute of Environmental
Health Sciences in Research Triangle Park, N.C.

"Our new results provide support for the idea that environmental factors may
increase susceptibility or trigger the development of autoimmune diseases in
some individuals," she says.

Although the study doesn't prove cause and effect, "we need to start
thinking about what chemicals or other factors related to insecticide use could
explain these findings," Parks tells WebMD.

The researchers used data from the Women's Health Initiative Observational
Study of 76,861 postmenopausal, predominantly white women ages 50 to 79. Of the
total, 178 of them had rheumatoid arthritis and 27 had lupus. An additional
eight women had both disorders. As part of the study, the women were asked a
number of questions relating to farming and insecticide use.

"Importantly, the relationships we observed were not explained by other
factors that we considered, including farm history, age, race, ethnicity,
socioeconomic factors such as education and occupation, smoking and other risk
factors for disease," Parks says.

Interestingly, a history of working or living on a farm did not appear to
increase risk of rheumatoid arthritis or lupus in the study, she adds. Previous
studies have linked farming and agricultural pesticide exposure to the
disorders.

The findings were presented at the annual meeting of the American College of
Rheumatology.

Studies show that as many as three-fourths of U.S. households have reported
using insecticides in the home or garden, and 20% of households have applied
insecticides in the last month, according to Parks.

"Insecticide exposure in the home can be quite persistent because they don't
break down in the home environment," Parks says.

"The findings are fairly compelling" because they show the greater and
longer the exposure, the greater the risk, says Darcy Majka, MD, assistant
professor of medicine at Northwestern University Feinberg School of
Medicine.

"Now we have to go back to the bench. Which products pose a risk? Is skin
exposure [to blame], or inhaling?" she says.

For now, Majka tells WebMD, "The important thing is to follow the directions
[on the product] and take other measures to limit chemical exposure."